Here is a vegetable and fruit planting guide for cooler regions for the month of May and a food garden checklist.
In the United States, late frost is possible this month in all or part of the states in the Northeast, Mid-Atlantic, eastern Pacific Northwest, Rocky Mountains and Plains regions. These regions include the U.S. Department of Agriculture Plant Hardiness Zones 4, 5, and 6.
Vegetables: Sow or plant out cool-weather crops when the danger of frost is past: broad beans, cauliflower, Brussels sprouts, carrots, onions, radishes, spinach, and parsnips. Harden off young plants from winter sowings of cauliflower, leeks, onions, lettuce, peas, and broad beans before planting out.
Make a second sowing of early peas. Support peas with sticks or netting.
Also when the danger of frost has passed, set out transplants of warm-weather crops: tomatoes and eggplants. Check seed packets to make sure that vegetables can be sown without protection.
Plant tomatoes in composted soil and with supports. Keep tomatoes well watered.
Celery can be planted at any time.
Make succession plantings of lettuce, beets, and carrots. These crops can be planted every 2 or 3 weeks from now until August to provide a constant supply.
Here are the distances apart (in inches) at which some seasonal vegetables should ultimately stand: carrots 2; beets 3; chard 6-8; corn 10-12; bush beans 4; lettuce 6-10; onions 2-3; peas 2-3; radishes 2; New Zealand spinach 12-18; turnips 3-4; spinach 3-4; rutabagas 4-5. Pole beans go into hills, 4 to 8 seeds to a hill and are later thinned to 2 or 3 plants.
Plant early potatoes, onion sets, and shallots. If you have extra room, try sweet potatoes.
Prepare and plant new asparagus beds. Harvest asparagus and early crops from cold frame.
Continue to sow in cold frames or beneath cloche for early crops where the danger of heavy frost is still present.
Maintenance: Side dressings of compost will help along seedlings.
A minor drought could come this month; be prepared to soak, not sprinkle.
Cultivate after watering. Shallow cultivation will keep the soil from crusting. Heavy rains and overhead irrigation will create the need for such work. Regular cultivation will stop weeds while they are young. If you find perennial weeds coming up, take them out. Don’t let the weeds get ahead of you.
Warm up the soil with cloches. Use horticultural fleece or floating cloches for early crops. Cloches will help warm up the soil and protect plants from insects.
Mulch when plants are several inches high.
Turn compost pile when it thaws.
Pests: Watch for insects and signs of disease. Keep an eye on potatoes for flea beetles. Horticultural fleece will protect plants from flea beetles.
Cutworms target seedlings and do a lot of damage now. Protect plants by placing cornmeal or bran meal around each plant. Cutworms eat the meal, which will swell inside the worm’s body and kill it.
Fruit trees and berries: Plant fruit trees, currants, raspberries and blackberries when the soil is workable. Plant new strawberries. Put cloches over strawberries if you want an early crop.
Thin the fruit on apples, pears, and plums when marble-size. Thin heavy-cropping nectarines and peaches when fruit is ½ inch (1-1.5 cm) in diameter. Spray apples and pears prone to scab infection. Paint the trunks of young fruit trees white or wrap trunks to prevent sunscald. Prune suckers and water sprouts from trees.
Prune back the stems of newly planted and two-year-old gooseberries by about one-half. Spray gooseberries and black currants for gooseberry mildew.
Feed summer-fruiting plants to promote good flowering and fruit. Fertilize or top-dress with compost established berries and grapes if not done last month.
Water new plantings deeply if weather is dry. Replace mulches removed last month. Control weeds around bush and cane fruit.
Watch for pests and signs of disease. Use sprays at dusk to avoid harming pollinating insects. Trap larvae on trunks of trees and destroy.
Cold frames and greenhouse: Begin sowing herbs. Pick out or pot up seedlings sown earlier.
Sow tender vegetables such as outdoor tomatoes and runner beans to plant out later, and cucumbers for greenhouse. Plant greenhouse tomato plants in large pots, or plant them in grow bags.
Increase ventilation on warm days. Check plants for signs of pests and disease, which often begin to multiply rapidly as the temperatures rise.